Narrative:

A large military training mission called mlat that we do once a year occurred in my airspace. Including simultaneous and separate aerial refueling K35's and 2 F35's each. A grand total of 6 aircraft orbiting in refueling tracks. The call signs of the F35's were aircraft X and aircraft Z. These two flights of two F35 aircraft requested to be cleared to refuel with their respective tankers around the same time. Clearance's where given and both flights of aircraft achieved their refueling and asked to be split up around the same time. Right before splitting; aircraft Y flight asked for a random a/right vector in the block 210b230 due to weather along the track. The request was granted. About this time the other tanker flight call sign aircraft a with aircraft Z tied on in the block fl170b190 requested end of a/right [aerial refueling] breakup and vectors to another military training area. As I was working on splitting aircraft a up; aircraft Y flight request breakup; I tell them to standby. I proceed to give aircraft a and aircraft Z instructions and accomplish ATC separation. Next thing I notice; aircraft X is splitting off from his aerial refueling heading and descending to another altitude not assigned by ATC. Aircraft X mistakenly took aircraft Z's instructions and didn't read back or verify any clearances. What lead to this event was the sector team being ill-informed of what will happen during this mission in the first place; including the call signs involved and the type of aerial work these aircraft would be requesting. We were told the majority of this mission would be conducted VFR or in grant county approach controls airspace. The call sign numbers were too similar as well. Why was this not coordinated and the numbers changed to prevent read back errors? This was the second night in a row that this mission was being run; and it did not run smoothly the first night with information being added and plans changing last minute. Management knew this from the night before. Aircraft were requesting to conduct work in a restricted area and we weren't sure they had permission to do so. The next day; this still wasn't cleared up. We did not have adequate staffing or preparation because management decided to cancel an extra person on overtime. Instead the manager came in to supervise the operation. The operation manager wasn't able to help due to the fact they were not rated on that sector nor able to coordinate or talk to the aircraft. This created a hazardous and confusing situation. It was not safe. First off; hold the military planning liaison accountable for last minute changes to the mission. Include a complete and thorough list of all participants and their requests. Many unclear situations could've been avoided if we knew who was able to operate in the R6714 yakima firing center and what aircraft were doing refueling where. Second; staffing; I had a d-side at the time; but later that evening when the midder's showed up. The military exercise only increased and our controllers had to work more volume and complex traffic than a typical mid and without extra staffing support. We were told the overtime was canceled because the mission was going to be conducted in other airspace and we had to save overtime money. Two nights in a row I worked a part of this mission that we weren't supposed to 'see'. The exercise don't ever go as planned and the prior evening was evidence to that. Our flm witnessed firsthand the uncoordinated additions to the mlat mission and yet did not provide the adequate staffing for the increased workload. They really dropped the ball on providing a safe NAS in the name of saving a few bucks.

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Original NASA ASRS Text

Title: Seattle Center Controller reported unsafe operations during a military exercise.

Narrative: A large Military training mission called MLAT that we do once a year occurred in my airspace. Including simultaneous and separate aerial refueling K35's and 2 F35's each. A grand total of 6 aircraft orbiting in refueling tracks. The call signs of the F35's were Aircraft X and Aircraft Z. These two flights of two F35 aircraft requested to be cleared to refuel with their respective tankers around the same time. Clearance's where given and both flights of aircraft achieved their refueling and asked to be split up around the same time. Right before splitting; Aircraft Y flight asked for a random A/R vector in the block 210B230 due to weather along the track. The request was granted. About this time the other Tanker flight call sign Aircraft A with Aircraft Z tied on in the block FL170B190 requested end of A/R [aerial refueling] breakup and vectors to another military training area. As I was working on splitting Aircraft A up; Aircraft Y flight request breakup; I tell them to standby. I proceed to give Aircraft A and Aircraft Z instructions and accomplish ATC separation. Next thing I notice; Aircraft X is splitting off from his aerial refueling heading and descending to another altitude not assigned by ATC. Aircraft X mistakenly took Aircraft Z's instructions and didn't read back or verify any clearances. What lead to this event was the sector team being ill-informed of what will happen during this mission in the first place; including the call signs involved and the type of aerial work these aircraft would be requesting. We were told the majority of this mission would be conducted VFR or in Grant County Approach Controls airspace. The call sign numbers were too similar as well. Why was this not coordinated and the numbers changed to prevent read back errors? This was the second night in a row that this mission was being run; and it did not run smoothly the first night with information being added and plans changing last minute. Management knew this from the night before. Aircraft were requesting to conduct work in a restricted area and we weren't sure they had permission to do so. The next day; this still wasn't cleared up. We did not have adequate staffing or preparation because management decided to cancel an extra person on overtime. Instead the manager came in to supervise the operation. The Operation Manager wasn't able to help due to the fact they were not rated on that sector nor able to coordinate or talk to the aircraft. This created a hazardous and confusing situation. It was not safe. First off; hold the military planning liaison accountable for last minute changes to the mission. Include a complete and thorough list of all participants and their requests. Many unclear situations could've been avoided if we knew who was able to operate in the R6714 Yakima Firing Center and what aircraft were doing refueling where. Second; staffing; I had a D-side at the time; but later that evening when the midder's showed up. The military exercise only increased and our controllers had to work more volume and complex traffic than a typical mid and without extra staffing support. We were told the overtime was canceled because the mission was going to be conducted in other airspace and we had to save overtime money. Two nights in a row I worked a part of this mission that we weren't supposed to 'see'. The exercise don't ever go as planned and the prior evening was evidence to that. Our FLM witnessed firsthand the uncoordinated additions to the MLAT mission and yet did not provide the adequate staffing for the increased workload. They really dropped the ball on providing a safe NAS in the name of saving a few bucks.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.